Semiconductor element and method for manufacturing the same

ABSTRACT

A semiconductor element includes a semiconductor layer, a carbide substrate, and a reflective layer. The carbide substrate is provided on the semiconductor layer. The reflective layer is provided on the carbide substrate such that the carbide substrate is sandwiched between the semiconductor layer and the reflective layer. The reflective layer includes silver and at least one of oxide particles and nitride particles.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2016-234596, filed Dec. 2, 2016. Thecontents of this application are incorporated herein by reference intheir entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a semiconductor element and to a methodfor manufacturing this semiconductor element.

Discussion of the Background

For example, a semiconductor light emitting element is known in which asemiconductor light emitting structure and electrodes are formed on asubstrate, and the resulting semiconductor light emitting element ismounted on a mounting board via eutectic solder. There is a method inwhich, when the substrate side of the light emitting element is fixed tothe mounting board, for example, in order to increase the output oflight in the semiconductor light emitting element, a reflective layer isprovided on the back of the substrate, thereby improving thereflectivity of light to the element structure side, and increasing thelight takeoff efficiency.

For example, JP-A 2005-72148 discloses a nitride-based semiconductorelement including a reflective layer which is composed of a metalmaterial such as silver and which is disposed on the rear face of acrystal substrate such as sapphire or SiC, an adhesive layer providedbetween the crystal substrate and the reflective layer, and a protectivelayer provided on the reflective layer opposite to the adhesive layer.

SUMMARY OF THE INVENTION

According to an embodiment of the present disclosure, a semiconductorelement includes a semiconductor layer, a carbide substrate, and areflective layer. The carbide substrate is provided on the semiconductorlayer. The reflective layer is provided on the carbide substrate suchthat the carbide substrate is sandwiched between the semiconductor layerand the reflective layer. The reflective layer includes silver and atleast one of oxide particles and nitride particles.

According to an embodiment of the present disclosure, a method formanufacturing a semiconductor element includes providing a semiconductorlayer on a carbide substrate, the carbide substrate having asemiconductor layer contact surface connected to the semiconductor layerand a reflective layer contact surface opposite to the semiconductorlayer contact surface. A reflective layer is provided on the reflectivelayer contact surface of the carbide substrate. The reflective layercontains silver and at least one of oxide particles and nitrideparticles.

BRIEF DESCRIPTION OF DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings.

FIG. 1A is a schematic bottom view showing the configuration of thesemiconductor light emitting element according to a first embodiment;

FIG. 1B is a schematic cross section showing the configuration of thesemiconductor light emitting element according to the first embodiment,and is a cross section along IB-IB′ line in FIG. 1A;

FIG. 2A is a schematic bottom view showing the configuration of thesemiconductor light emitting element according to a second embodiment;

FIG. 2B is a schematic cross section showing the configuration of thesemiconductor light emitting element according to the second embodiment,and is a cross section along IIB-IIB′ line in FIG. 1A;

FIG. 3A is a schematic detail cross section of the state of an oxide ora nitride and the interface between the carbide substrate and thereflective layer of the semiconductor light emitting element accordingto the first and second embodiments;

FIG. 3B is a schematic detail cross section of the state of an oxide ora nitride and the interface between the carbide substrate and thereflective layer of the semiconductor light emitting element accordingto the first and second embodiments;

FIG. 4 is a flowchart showing the flow of the method for manufacturingthe semiconductor light emitting element according to the firstembodiment;

FIG. 5A is a photograph of the sample in Working Example 1 taken fromthe film formation side;

FIG. 5B is a photograph of the sample in Working Example 2 taken fromthe film formation side;

FIG. 5C is a photograph of the sample in Working Example 3 taken fromthe film formation side;

FIG. 5D is a photograph of the sample in Working Example 4 taken fromthe film formation side;

FIG. 5E is a photograph of the sample in Working Example 5 taken fromthe film formation side;

FIG. 5F is a photograph of the sample in Working Example 6 taken fromthe film formation side;

FIG. 5G is a photograph of the sample in Comparative Example 1 takenfrom the film formation side; and

FIG. 5H is a photograph of the sample in Comparative Example 2 takenfrom the film formation side.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

First Embodiment

Embodiments will now be described through reference to the drawings.However, the modes given below are illustrative of a semiconductorelement for embodying the technical idea of these embodiments, andembodiments are not limited to those that follow. Also, unless otherwisespecified, the dimensions, materials, shapes, relative layouts, and soforth of the constituent elements given in the following embodiments aremerely illustrative and are not intended to limit the scope of thepresent invention. Furthermore, the sizes, positional relations, and soforth of the members shown in the drawings may be exaggerated forclarity.

Semiconductor Element

First, the semiconductor element according to the first embodiment willbe described. The semiconductor element according to the firstembodiment is a semiconductor light emitting element.

FIG. 1A is a schematic bottom view showing the configuration of thesemiconductor light emitting element according to the first embodiment.FIG. 1B is a schematic cross section showing the configuration of thesemiconductor light emitting element according to the first embodiment,and is a cross section along IB-IB′ line in FIG. 1A. FIGS. 3A and 3B areschematic detail cross sections of the state of an oxide or a nitrideand the interface between the carbide substrate and the reflective layerof the semiconductor light emitting element according to the first andsecond embodiments. In FIGS. 3A and 3B, the state of the oxide ornitride in the reflective layer is depicted in schematic form to make iteasier to understand. Further, the part labeled B in FIGS. 3A and 3B isa schematic view of a pseudo transition layer.

Semiconductor Layer and Electrode

A semiconductor light emitting element 100 includes an n-type nitridesemiconductor layer 2, a light emitting layer 3, a p-type nitridesemiconductor layer 4, and a p-side full-surface electrode 5, on a firstmain face of a carbide substrate 1. The semiconductor light emittingelement 100 also includes a p-side pad electrode 6 in a partial regionon the p-side full-surface electrode 5. The p-type nitride semiconductorlayer 4, the p-side full-surface electrode 5, and the p-side padelectrode 6 are electrically connected. Also, a reflective layer 7 thatalso serves as an n-side full surface electrode is provided on a secondmain face opposite to the first main face of the carbide substrate 1.The reflective layer 7 that also serves as an n-side full surfaceelectrode is electrically connected to the n-type nitride semiconductorlayer 2.

In_(X)Al_(Y)Ga_(1-X-Y)N (0≤X, 0≤Y, X+Y<1) or the like can be used toadvantage as the material of the semiconductor layer, for example. Thep-side full-surface electrode 5 is formed from a conductive oxide.Examples of conductive oxides include oxides of one or more members ofthe group consisting of zinc, indium, tin, and magnesium, and morespecific examples include ZnO, In₂O₃, SnO₂, and indium tin oxide (ITO).The material of the p-side pad electrode 6 can be, for example, silver,aluminum, nickel, rhodium, titanium, platinum, palladium, molybdenum,chromium, tungsten, copper, gold, or another such elemental metal, oralloys whose main components are these metals. Alternatively, it canalso be a laminated structure made from the above-mentioned elementalmetals or an alloy whose main components are these metals.

Carbide Substrate

There are no particular restrictions on the carbide substrate 1, but anSiC substrate is an example of a substrate on which a nitridesemiconductor is grown, for example.

The front (first main face) or rear (second main face) of the carbidesubstrate 1 may be flat, but it may be worked into a textured shape toenhance the light takeoff efficiency. The semiconductor layer may alsobe formed on the first main face of the carbide substrate 1 via a masklayer, a buffer layer, an intermediate layer, or the like.

Reflective Layer

The reflective layer 7 is a silver alloy layer containing one or moretype of particles selected from among oxides and nitrides, and is alayer for improving the light takeoff efficiency by increasing thereflectivity of light to the element structure side. The reflectivelayer 7 also functions as an n-side full-surface electrode. Theparticles contained in the silver alloy layer may be only oxideparticles or only nitride particles, but may also be a mixture of oxideparticles and nitride particles. These particles will be referred to asthe “oxide or nitride 9” here. The reflective layer 7 is preferablyprovided over the entire lower face of the carbide substrate 1. Theoxide or nitride 9 is uniformly dispersed in the reflective layer 7.Since the reflective layer 7 includes the oxide or nitride 9, a pseudotransition layer in which both the oxide or nitride 9 and the silver inthe reflective layer 7 are present will be provided at the interfacebetween the reflection layer 7 and the carbide substrate 1. Providingthis pseudo transition layer improves adhesion between the carbidesubstrate 1 and the reflective layer 7, and gives a semiconductor lightemitting element 100 with higher reliability.

Here, saying that both the oxide or nitride 9 and the silver in thereflective layer 7 are present at the interface between the reflectionlayer 7 and the carbide substrate 1 refers to a state in which part ofthe oxide or nitride 9 is present at the interface, and the oxide ornitride 9 is in contact with the carbide substrate 1 along with thesilver. Also, “pseudo transition layer” does not mean that a layer isactually formed, and merely refers to a state in which the presence ofsilver and the oxide or nitride 9 at the interface allows these toapproximate a layer formed at the interface.

Also, when the oxide or nitride 9 is present in the reflective layer 7,this results in a pinning effect, which suppresses the growth of crystalgrains of the silver that is the main component of the reflective layer7. This makes it less likely that crystal grains will grow due to theheat history from the step of assembling the semiconductor element,which keeps the surface of the reflective layer 7 smooth, or suppressesthe generation of voids in the reflective layer 7. Therefore, thereflective layer 7 is more likely to maintain high reflectivity and heatdissipation.

The oxide or nitride 9 is dispersed in particulate form in thereflective layer 7, or adheres to the interface between the reflectivelayer 7 and the carbide substrate 1. Here, the oxide or nitride 9adhering to the interface between the reflection layer 7 and the carbidesubstrate 1 does not form a layer of just the oxide or nitride 9, andpart of the silver must be in contact with the carbide substrate 1.However, as long as some of the silver is in contact with the carbidesubstrate 1, the oxide or nitride 9 may be linked in a reticulated form.When the added amount of oxide or nitride 9 is small, there will tend tobe little adhesion of the oxide or nitride 9 at the interface, and theoxide or nitride 9 resulting in a pseudo transition layer in which theoxide or nitride 9 is formed as islands. The term “islands” means thatthe oxide or nitride 9 is not contiguous, and is instead present as dotshere and there. Here again, since the oxide or nitride 9 and the silverare both present, it can be said that a pseudo transition layer isformed.

The oxide or nitride 9 in the reflective layer 7 is preferably one ormore substances selected from among Si₃N₄, ZnO, TiO₂, Ta₂O₅, HfO₂,In₂O₃, Nb₂O₅, SiO₂, AlN, SnO₂, NiO, Al₂O₃, ZrO₂, Ga₂O₃, and GaN. Fromthe standpoint of adhesion to the carbide substrate 1, the oxide ornitride 9 in the reflective layer 7 is more preferably one or moresubstances selected from among Si₃N₄, ZnO, TiO₂, Ta₂O₅, HfO₂, and In₂O₃.

It is preferable that the content of the oxide or nitride 9 in thereflective layer 7 is greater than 0.001 wt % with respect to the totalweight of the reflective layer 7. Having the oxide or nitride 9 exceed0.001 wt % improves the adhesion between the reflective layer 7 and thecarbide substrate 1. From the standpoint of adhesion to the carbidesubstrate 1, the content of the oxide or nitride 9 in the reflectivelayer 7 is preferably at least 0.01 wt %, and more preferably at least0.02 wt %. Also, from the standpoint of the reflectivity (initialreflectivity) of the reflective layer 7, the content of the oxide ornitride 9 in the reflective layer 7 is preferably no more than 5 wt %,more preferably no more than 4 wt %, and even more preferably no morethan 2.5 wt %.

The higher is the transparency of the oxide or nitride 9 contained inthe reflective layer 7, the higher is the reflectivity, so the higher isthe transparency of the oxide 9, the more the content of the oxide ornitride 9 may be increased.

The content of the oxide or nitride 9 in the reflective layer 7 can bemeasured by inductively coupled plasma atomic emission spectrometry(ICP-AES) or the like.

Operation of Semiconductor Light Emitting Element

The operation of the semiconductor light emitting element 100 will nowbe described through reference to FIG. 1B.

With the semiconductor light emitting element 100, the light emittinglayer 3 emits light when current is supplied to a semiconductor layer 20via the reflective layer 7 and the p-side pad electrode 6. The lightemitted from the light emitting layer 3 propagates through thesemiconductor layer 20 and the carbide substrate 1, and light travelingupward in the drawing is taken off to the outside from the semiconductorlayer 20 side (element structure side). Light traveling downward in thedrawing is reflected upward by the reflecting layer 7 and taken off fromsemiconductor layer 20 side to the outside.

Method for Manufacturing Semiconductor Light Emitting Element

Next, a method for manufacturing the semiconductor light emittingelement according to the first embodiment will be described. FIG. 4 is aflowchart showing the flow in the method for manufacturing asemiconductor light emitting element according to the first embodiment.

The method for manufacturing the semiconductor light emitting element100 in the first embodiment includes, for example, a semiconductor layerformation step S101, an electrode formation step S102, a laser scribingstep S103, a reflective layer formation step S104, and a wafer divisionstep S105, in that order. The materials, layout, and so forth of thevarious members is the same as in the above description of thesemiconductor light emitting element 100, and therefore may not bedescribed again.

Semiconductor Layer Formation Step, Electrode Formation Step

The semiconductor layer formation step S101 is a step of forming thesemiconductor layer 20 on the first main face of the carbide substrate1, which includes a first main face and a second main face opposite tothe first main face. The electrode formation step S102 is a step offorming electrodes, such as the p-side full-surface electrode 5 and thep-side pad electrode 6, on the semiconductor layer 20. The semiconductorlayer 20 and the electrodes are formed by a known manufacturing method;for example, they can be formed by the following method.

The semiconductor layer 20 is produced by using an MOVPE reaction deviceto grow semiconductors that will constitute the n-type nitridesemiconductor layer 2, the light emitting layer 3, and the p-typenitride semiconductor layer 4, in that order, on the first main face ofthe carbide substrate 1.

After this, an ITO film, for example, is formed as the p-sidefull-surface electrode 5 with a sputtering device over the entiresurface of the wafer. A resist mask is then formed and etching isperformed so as to leave the ITO film on almost the entire surface ofthe p-type nitride semiconductor layer 4, after which the resist isremoved. Next, a mask that is open in specific regions over the p-sidefull-surface electrode 5 is formed with a photoresist. A sputteringdevice is then used to form a metal film continuously and sequentiallyfor a pad electrode over the wafer. The resist is then removed(lift-off) to form the p-side pad electrode 6. After this, the wafer isground or polished on a different side from the side on which the p-sidepad electrode 6 was formed, to smooth out any bumps.

Laser Scribing Step

The laser scribing step S103 is a step of producing the sites where thewafer is to be diced by laser irradiation (cutting regions). First, thewafer to be diced is irradiated with laser light from the carbidesubstrate 1 side so as to focus on the interior of the carbide substrate1 in the cutting regions. This form modified portions inside thesubstrate 1. These modified portions are breaking grooves extending inthe thickness direction of the substrate 1, that is, a directionsubstantially perpendicular to the first main face of the substrate 1.An example of the laser light used here is a femtosecond laser.

Reflective Layer Formation Step

The reflective layer formation step S104 is a step of forming thereflective layer 7, containing the oxide or nitride 9 and having silveras its main component, on the second main face of the carbide substrate1.

An example in which an oxide is contained in the reflective layer 7 willbe described. If a nitride is to be used, just replace “oxide” with“nitride.” For example, the layer can be formed by co-sputtering usingan oxide target and a silver target, sputtering using an alloy targetcontaining silver and an oxide, or vapor deposition using an alloy vapordeposition material containing silver and an oxide. These sputtering andvapor deposition methods can be used to form a reflective layer 7 inwhich an oxide is dispersed in the reflective layer 7.

The alloy used for the alloy target or alloy vapor deposition materialhas silver as its main component, and is an alloy that includes theoxide 9 in silver. Here, the oxide 9 is dispersed as nanoparticles inthe silver. In addition to the use of an alloy vapor depositionmaterial, the vapor deposition can be performed using a method in whichthe reflective layer 7 is formed by using a vapor deposition materialcomposed of silver and a vapor deposition material composed of the oxide9, and simultaneously vapor depositing these materials. The silver usedin the sputtering or vapor deposition can also be pure silver.

The other conditions, procedures, and so forth entailed in sputtering orvapor deposition can be the same as in known methods.

Wafer Division Step

Next, the wafer is cut in the cutting regions and the individualsemiconductor light emitting elements are divided into chips. The waferdivision step S105 is a step of dividing the wafer on which thesemiconductor layer 20, the electrodes, and the reflective layer 7 areformed into chips.

The semiconductor light emitting element 100 can be manufactured throughthe above steps.

Second Embodiment

Next, a semiconductor element according to the second embodiment will bedescribed. The semiconductor element according to the second embodimentis a semiconductor light emitting element. FIG. 2A is a schematic bottomview showing the configuration of the semiconductor light emittingelement according to the second embodiment. FIG. 2B is a schematic crosssection showing the configuration of the semiconductor light emittingelement according to the second embodiment, and shows a cross sectionalong the IIB-IIB′ line in FIG. 2A. FIGS. 3A and 3B are schematic crosssections of the state of the oxide or nitride and the interface betweenthe reflective layer and the carbide substrate of the semiconductorlight emitting element according to the second embodiment.

Those components that are the same as in the first embodiment will notbe described again.

Semiconductor Layer and Electrodes

The semiconductor light emitting element 200 includes a p-type nitridesemiconductor layer 104, a light emitting layer 103, and an n-typenitride semiconductor layer 102, which are laminated via an adhesivelayer 110 on the first main face of a carbide substrate 101.Furthermore, the semiconductor light emitting element 200 includes ann-side pad electrode 108 in part of the region on the n-type nitridesemiconductor layer 102. It also includes a reflective layer 107, whichalso serves as a p-side full-surface electrode, on the second main faceof the carbide substrate 101 opposite to the first main face.

As in the first embodiment, In_(X)Al_(Y)Ga_(1-X-Y)N (0≤X, 0≤Y, X+Y<1) orthe like can be used to advantage, for example, as the material of thesemiconductor layer. Silver, aluminum, nickel, rhodium, titanium,platinum, palladium, molybdenum, chromium, tungsten, copper, gold, oranother such elemental metal, or alloys whose main components are thesemetals, can be used, for example as the material of the n-side padelectrode 108. Alternatively, it can also be a laminated structure madefrom the above-mentioned elemental metals or an alloy whose maincomponents are these metals.

Carbide Substrate

The carbide substrate 101 is a joining substrate to be joined to theelement structure separated from the crystal growth substrate. If thesubstrate is electroconductive, it is possible to employ an upper andlower electrode (counter electrode) structure. Also, it will be easierto supply power to the element structure uniformly in the plane, and thepower efficiency will tend to be higher. Examples of the carbidesubstrate 101 include an SiC substrate with excellent thermalconductivity and electrical conductivity.

Joining Layer 110

The joining layer 110 is a layer that joins the carbide substrate 101(the above-mentioned joining substrate) to a semiconductor layer 120that is separated from the crystal growth substrate. This joining layer110 preferably includes a metal reflective film or a dielectricmultilayer film. Consequently, with the semiconductor light emittingelement 200, light emitted from the element structure can be efficientlyreflected upward by the metal reflective film or the dielectricmultilayer film of the joining layer 110, and light emitted from theelement structure will be less likely to travel through the interior ofthe substrate, allowing the light takeoff efficiency to be increased.Providing the metal reflective film or dielectric multilayer film of thejoining layer 110 in contact with the element structure, or in contactwith a transparent film such as a conductive oxide film provided incontact with the element structure, is preferable since its lightreflection function will be enhanced. The metal reflective film used inthe joining layer can be made of silver, aluminum, rhodium, platinum,gold, or an alloy of these, and the preferably, silver or a silver alloyis used because of their superior optical reflectivity. The dielectricmultilayer film used in the joining layer can be, for example, theproduct of laminating two or more layers of one or more oxides ornitrides selected from among silicon, titanium, zirconium, niobium,tantalum, and aluminum, such as a laminated structure of Nb₂O₅ and SiO₂.The metal reflective film is provided to all or part of the joininglayer, and the dielectric multilayer film is provided to part of thejoining layer. When a metal reflective film or a dielectric multilayerfilm is provided to part of the joining layer, the other part of thejoining layer can be constituted by gold, tin, platinum, palladium,rhodium, nickel, tungsten, molybdenum, chromium, titanium, alloys ofthese, or a combination thereof. The joining layer can be omitted whenthe substrate that is the joining substrate and the element structurethat is separated from the crystal growth substrate are directly joinedby surface activation joining, thermocompression joining, or the like.

Reflective Layer 107

The reflective layer 107 is the same as in the first embodiment. It is asilver alloy layer containing one or more types of particles selectedfrom among oxides and nitrides, and is a layer that improves the lighttakeoff efficiency by increasing the reflectivity of light to theelement structure side. It also functions as a p-side full-surfaceelectrode. The reflective layer 107 may be a multilayer film or asingle-layer film. The reflective layer 107 can be formed by sputtering,plating, vapor deposition, or another such method. The oxide or nitride109 contained in the reflective layer 107 is distributed in granularform in the reflective layer 107, or adheres to the interface betweenthe reflective layer 107 and the carbide substrate 101.

WORKING EXAMPLES

Working examples will now be given. FIGS. 5A to 5H are photographs takenfrom the film formation side after cross-cutting the film formationfaces in Working Examples 1 to 6 and Comparative Examples 1 and 2.

Working Example 1

Adhesion evaluation samples were prepared as follows.

First, a reflective layer containing Si₃N₄ was formed in a thickness of120 nm by co-sputtering using a silver target and an Si₃N₄ target, onthe C plane of an SiC single crystal substrate. The RF power was 250 Win both cases of the simultaneous sputtering. Also, a nickel film wasformed as a first metal film in a thickness of 100 nm, a rhodium filmwas formed as a second metal film in a thickness of 200 nm, and a goldfilm was formed as a third metal film in a thickness of 500 nm, in thatorder, by sputtering on the reflective layer. This formed a laminatedfilm on the C plane of the SiC single crystal substrate.

Working Example 2

In the manufacturing process of Working Example 2, the light emittingelement of Working Example 2 was manufactured in the same manner as inWorking Example 1, except that a reflective layer containing ZnO wasformed instead of the reflective layer containing Si₃N₄ of WorkingExample 1. The reflective layer containing ZnO was formed byco-sputtering using a silver target and a ZnO target. The RF power was250 W in both cases of the simultaneous sputtering.

Working Example 3

In the manufacturing process of Working Example 3, the light emittingelement of Working Example 3 was manufactured in the same manner as inWorking Example 1, except that a reflective layer containing TiO₂ wasformed instead of the reflective layer containing Si₃N₄ of WorkingExample 1. The reflective layer containing TiO₂ was formed byco-sputtering using a silver target and a TiO₂ target. The RF power was250 W in both cases of the simultaneous sputtering.

Working Example 4

In the manufacturing process of Working Example 4, the light emittingelement of Working Example 4 was manufactured in the same manner as inWorking Example 1, except that a reflective layer containing Ta₂O₅ wasformed instead of the reflective layer containing Si₃N₄ of WorkingExample 1. The reflective layer containing Ta₂O₅ was formed byco-sputtering using a silver target and a Ta₂O₅ target. The RF power was250 W in both cases of the simultaneous sputtering.

Working Example 5

In the manufacturing process of Working Example 5, the light emittingelement of Working Example 5 was manufactured in the same manner as inWorking Example 1, except that a reflective layer containing HfO₂ wasformed instead of the reflective layer containing Si₃N₄ of WorkingExample 1. The reflective layer containing HfO₂ was formed byco-sputtering using a silver target and an HfO₂ target. The RF power was250 W in both cases of the simultaneous sputtering.

Working Example 6

In the manufacturing process of Working Example 6, the light emittingelement of Working Example 6 was manufactured in the same manner as inWorking Example 1, except that a reflective layer containing In₂O₃ wasformed instead of the reflective layer containing Si₃N₄ of WorkingExample 1. The reflective layer containing In₂O₃ was formed byco-sputtering using a silver target and an In₂O₃ target. The RF powerwas 250 W in both cases of the simultaneous sputtering.

Comparative Example 1

In the manufacturing process of Comparative Example 1, the lightemitting element of Comparative Example 1 was manufactured in the samemanner as in Working Example 1, except that a pure silver layer wasformed instead of the reflective layer containing Si₃N₄ of WorkingExample 1. The pure silver layer was formed by sputtering using only asilver target. The RF power was 500 W in this sputtering.

Comparative Example 2

In the manufacturing process of Comparative Example 2, the lightemitting element of Comparative Example 2 was manufactured in the samemanner as in Working Example 1, except that a reflective layercontaining TiC was formed instead of the reflective layer containingSi₃N₄ of Working Example 1. The reflective layer containing TiC wasformed by co-sputtering using a silver target and a TiC target. The RFpower was 250 W in both cases of the simultaneous sputtering.

The film formation faces of the samples from the above Working Examples1 to 6 and Comparative Examples 1 and 2 were cross-cut (JIS K 5600). Theappearance after tape peeling was observed from the film formation side.Observation was performed using a Keyence Digital Microscope VHX-700F ata power of 25.

As a result, with Comparative Examples 1 and 2, a large amount pulledaway at the interface between the SiC single crystal substrate and thereflective layer, whereas with Working Examples 1 to 6, there was nopeeling of the respective reflective layer containing Si₃N₄, thereflective layer containing ZnO, the reflective layer containing TiO₂,the reflective layer containing Ta₂O₅, the reflective layer containingHfO₂, and the reflective layer containing In₂O₃. In the photographs ofComparative Examples 1 and 2 in FIGS. 5G and 5H, those areas ofdifferent brightness other than the cross-cut portions, as compared tothe photographs of Working Examples 1 to 6, are areas where peelingoccurred.

Thus, with the semiconductor element in the embodiments disclosedherein, there is good adhesion between the carbide substrate and thereflective layer, and separation is less likely to occur at thereflective layer. Also, with the method for manufacturing asemiconductor element in the embodiments disclosed herein, asemiconductor element can be manufactured with which there is goodadhesion between the carbide substrate and the reflective layer, andseparation is less likely to occur at the reflective layer.

The semiconductor element and semiconductor element manufacturing methodaccording to the present invention were described in specific termsabove by embodiments of the invention, but the gist of the presentinvention is not limited to or by these descriptions, and should beinterpreted broadly based on the description of the patent claims. Also,it should go without saying that various modifications, alterations, andso forth based on these descriptions are also included in gist of thepresent invention.

INDUSTRIAL APPLICABILITY

The semiconductor element according to the embodiments disclosed hereincan be utilized in all semiconductor light emitting devices that makeuse of light emitting elements, such as various kinds of lightingfixture, automotive lighting, displays, and indicator. Also, in additionto devices that make use of light elements such as light receivingdevices, the present invention can also be applied to a power transistoror other such a semiconductor device or semiconductor electronic device.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A semiconductor element comprising: asemiconductor layer; a joining layer provided on the semiconductorlayer; a carbide substrate provided on the joining layer, the joininglayer being provided between the semiconductor layer and the carbidesubstrate so as to be in contact with both of the semiconductor layerand the carbide substrate; and a reflective layer provided on thecarbide substrate such that the carbide substrate is sandwiched betweenthe joining layer and the reflective layer, the reflective layercomprising: silver; and at least one of oxide particles and nitrideparticles provided at an interface between the reflective layer and thecarbide substrate, the at least one of the oxide particles and thenitride particles being in contact with the carbide substrate along withthe silver, wherein the joining layer comprises a metal reflective film.2. The semiconductor element according to claim 1, wherein the at leastone of oxide particles and nitride particles is provided on or in avicinity of a boundary between the carbide substrate and the reflectivelayer.
 3. The semiconductor element according to claim 1, wherein the atleast one of oxide particles and nitride particles are dispersed in thereflective layer.
 4. The semiconductor element according to claim 1,wherein the at least one of oxide particles and nitride particles aredistributed in a vicinity of a boundary between the carbide substrateand the reflective layer.
 5. The semiconductor element according toclaim 1, wherein the amount in which the at least one of oxide particlesand nitride particles are contained in the reflective layer is at least0.01 wt % and no more than 5 wt % with respect to the total weight ofthe reflective layer.
 6. The semiconductor element according to claim 1,wherein the at least one of the oxide particles and nitride particlesinclude at least one of Si₃N₄, ZnO, TiO₂, Ta₂O₅, HfO₂, and In₂O₃.
 7. Thesemiconductor element according to claim 1, wherein the semiconductorelement is a semiconductor light emitting element.
 8. The semiconductorelement according to claim 1, wherein the carbide substrate is providedon the semiconductor layer via another layer.
 9. The semiconductorelement according to claim 1, wherein the reflective layer is directlyprovided on the carbide substrate.
 10. The semiconductor elementaccording to claim 1, wherein the semiconductor layer comprises ann-type nitride semiconductor layer, a light emitting layer, and a p-typenitride semiconductor layer, and the joining layer being providedbetween the p-type nitride semiconductor layer and the carbide substrateso as to be in contact with both of the p-type nitride semiconductorlayer and the carbide substrate.
 11. The semiconductor element accordingto claim 1, wherein the metal reflective film made of a same metal as ametal contained in the reflective layer.
 12. The semiconductor elementaccording to claim 1, wherein the metal reflective film is made ofsilver, aluminum, rhodium, platinum, gold, or an alloy of silver,aluminum, rhodium, platinum, or gold.
 13. The semiconductor elementaccording to claim 1, wherein the reflective layer comprises silver anda mixture of oxide particles and nitride particles.
 14. Thesemiconductor element according to claim 1, wherein, at the interfacebetween the reflective layer and the carbide substrate, the at least oneof the oxide particles and the nitride particles is linked in areticulated form.
 15. The semiconductor element according to claim 1,wherein, at the interface between the reflective layer and the carbidesubstrate, a pseudo transition later is disposed in which the at leastone of the oxide particles and the nitride particles is formed asislands.
 16. A semiconductor element comprising: a semiconductor layer;a carbide substrate provided on the semiconductor layer; and areflective layer provided on the carbide substrate such that the carbidesubstrate is sandwiched between the semiconductor layer and thereflective layer, the reflective layer comprising: silver; and a mixtureof oxide particles and nitride particles provided at an interfacebetween the reflective layer and the carbide substrate, the mixture ofthe oxide particles and the nitride particles being in contact with thecarbide substrate along with the silver.
 17. The semiconductor elementaccording to claim 16, wherein, at the interface between the reflectivelayer and the carbide substrate, the at least one of the oxide particlesand the nitride particles is linked in a reticulated form.
 18. Thesemiconductor element according to claim 16, wherein, at the interfacebetween the reflective layer and the carbide substrate, a pseudotransition later is disposed in which the at least one of the oxideparticles and the nitride particles is formed as islands.